Steam blanchers and chilled water coolers have long been used in the food processing industry to blanch, cook, or cool a continuous throughput of food product such as pasta, green peas, corn, beans and other processed food products. Helical augers mounted within a perforated drum suspended in a water-filled tank have long been used to good effect. The perforated steel screen skin of the drum allows water to flow freely into the interior of the drum, and the auger within the drum gently advances food product from the tank inlet to the tank discharge end as the dram is rotated.
At one time, augers for such apparatus were mounted on a central drive shaft and were driven directly by an engaged sprocket and motor. A central drive shaft, however, presented several problems. First, the extension of the drive shaft axially through the inlet end of the tank interfered with the introduction of food product into the cylindrical drum. Furthermore, food product coming into contact with the central shaft was subject to damage. In addition, experience showed that central drive shafts of narrow diameter were prone to breakage.
Subsequent rotatable drum coolers and blanchers eliminated the breakage problem of the central drive shaft by mounting the helical auger flights on a central cylindrical core which extended through the inlet and outlet ends of the blancher tank to define cylindrical journals which were supported on two rotatable trunnions at each end. The cylindrical core in this type of apparatus is of sufficient diameter to allow the introduction of an infeed chute through the inlet journal. To allow the food product to pass into and exit from the cylindrical drum, the core is replaced at the inlet and outlet ends of the drum with a number of structural steel bars symmetrically spaced a distance from the rotational axis of the drum equal to the radius of the core. These bars provided admirable stiffness and did not interfere with the introduction of the infeed chute, although sometimes did conflict with the introduction of delicate food product.
An apparatus which provided no interference with infed food product was disclosed in my own prior U.S. Pat. No. 5,146,841, to an open-throat blancher. This apparatus utilized a drum composed of supporting C-channels which contributed to the carrying of the loads of the auger along with the assistance of a central core tube which was rigidly fixed to the end plate.
Food processing machine, which is typically subjected to varying extremes of temperature, liquids, and organic contaminates, must be highly resistant to corrosion. To address this need blanchers and coolers are commonly fabricated of stainless steel, a material which is not only costly by weight, but which requires skilled craftsmanship to work.
What is needed is a rotating drum food processing apparatus which may be manufactured at reduced cost yet which does not suffer in performance.